Does anyone know of a mobile linear amplifier that will work on 6 meter, 2 meter, 1.25 meter and 70 CM? I am looking for an amplifier for a Yaesu VX-8R HT.
I am not aware of a hobby purposed single amplifier for this application you could find at any Ham vendor. That does not mean you could not get it done though.
As an example you might grab a multiplexer and break out each band individually, taking them each to a single band amplifier. Something like the Diamond MX324, with an MX62M on the LPF port. The M324 would give you three outputs, 6M and 2M on Port 1, 1.25M on Port 2, and 70cm on Port 3. You would then take the Port 1 signal and apply it to the input of the MX62M, yielding 6M on Port 1 of the 62M and 2M on Port 2.
So each band will now be on a separate feedline (with the isolation of the multiplexers). You could also play with combinations to yield dual band operations, say if you wanted to combine 2M / 70cm into a single amp or antenna.
While not this exact combination, I have done the same thing to break out 10M, 6M, 2M, and 70 cm from an FT-8900R and other wideband, single output, radios. I am generally not a fan of multiband antennas, and so I wanted a mono band antenna for each band in a specific application. It seemed to work pretty well, the losses through the multiplexers I used appeared to not impact performance (specification for each of them was less than 0.4 dB), and the band-to-band isolation seemed pretty good (specifications typically 50+ dB).
T!